Disintegrating sabot



March 1969 R. HEBERT ETAL & 3 57 DISINTEGRATING SABOT Filed Nov. 22. 1966 JOHN R. HEBERT WARREN A.WA|TE INVENTORS ;F ;94 cm #4 ATTOR NE YS 4 United States Parent 8 Claims `ABSTRACT OF THE DISCLOSURE The invention relates to a sabot for a gas propelled projectile. The sabot is constructed in such a manner that it traps a quantity of the propellant gas internally in pores. The pressure of the entrapped gas induces a stress greater than the tensile strength of the sabot material and When the sabot and projectile leave the confines of a muzzle, the sabot explodes and disintegrates.

This invention relates to sabots used in connection with projectles for producing high muzzle velocities in projectiles. And more particularly, the invention relates to a sabot that disintegrates on leaving the gun barrel.

It is well known that the penetrating ability of a projectile can be greatly increased if the ratio of the diameter to the mass of the projectiles is small. On the other hand, the use of such small projectiles often creates serious problems with regard to adopting the projectiles to existing weapons and with regard to achieving a high velocity in a limited length of time-limited by the length of an existing gun barrel-because of the small area presented to the propellant.

The sabot oifers a workable solution to both of these problems since it provides an increased area on which the propellant can act. Also, the diameter of the sabot can be made to match the calibre of existing weapons.

'Ihe use of sabots introduces problems not the least of which are aerodynamic instability, and Ieduced range, if the sabot remains attached to the projectile too long after both the sabot and the projectile leave the gun barrel.

It is an object of the invention to provide a sabot which avoids the limitations and disadvantages of previously known sabots.

It is another object of the invention to provide a disintegrating sabot.

It is a further object of the invention to provide a very high pressure gradient in the sabot structure for causing disintegration of the sabot at an appropriate time.

It is a further object of the invention to provide a porous structured sabot 'for entrapping high pressure propellant gas.

It is another object of the invention to provide a disintegrating sabot having a controlled tensile strength and means for internally entrapping high pressure gases whereby the gases overcome the tensile stren-gth causing disintegration at the predetermined time.

In accordance with the invention, a sabot for use with a projectile comprises a porous structure having openings adapted to communicate with propellant gas. The gas defuses within the porous structure creating a high internal pressure gradient so that when the projectile and sabot emerge from a gun barrel, the entrapped high pressure gas causes the sabot to rupture and disintegrate.

The novel features that are considered characteristic of the invention are set forth in the appended claims; the invention itself, however, both as to its organization and method of operation, together with addtional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in conjunction with the accompanying drawings, in' which:

3,430,572 Patented Mar. 4, 1969 FIGURE 1 shows a projectile sabot combination totally enclosed in a gun barrel;

FIGURE 2 shows a sabot projectile combination emerging from a gun barrel;

FIGURE 3 shows the sabot disintegrating; and

FIGURE 4 shows alternate sabot constructons.

Referring to FIGURE 1, there is shown a portion of a gun barrel 11, a projectile 12 typically having a small diameter to mass ratio, and a porous sabot 13. In the FIGURE 1 illustration the sabot is constructed preferably from an open cell expanded foam. Foam is ideally suited for this application because of its generally homogeneous structure, and low tensile strength which can be accurately designed and controlled.

The propellant gas is depicted by arrows 14 which generally show the gas entering the porous sabot structure during the course of time that it takes the sabot and projectile to travel through the gun 'barrel. The sabot is secured to the projectile by means of threads 16.

In FIGURE 2, the combination of projectile and sabot is shown emerging from the muzzle of a gun barrel 11. The arrows 14a show the propellant gases escaping from the muzzle around the outside of the sabot 13. The arrows 14b represent the entrapped propellant gas attempting to leave the porous sabot 13-.

The propellant gases, of course, exist at extremely high pressure in the order of several thousand pounds per square inch. When these gases were entrapped in the sabot 13, they were entrapped at this high pressure. The sabot resists physical deformation because it is supported by the gun barrel walls. Clearly, when the sabot emerges from the gun barrel, there is immediately set up a pressure gradient between the extremely high pressure entrapped in the sabot and atmospheric pressure at the surface of the sabot. The attempted escape of the high pressure gas and the high pressure gradient causes the sabot to disintegrate in all directions uniformly as shown in FIGURE 3.

The forward momentum is not materially aifected since the disintegrated force is unform over the surface of the projectile and it is generally a lateral force. While the disintegrating forces do not generally introduce aerodynamic instabilities, should such instabilities arise these instabilities occur at the very start of the ballistic fiight and act for an extremely short time thus enabling the stabilizing influences on the projectile to work effectively.

It is quite clear that a disintegrating structure may be provided by means other than a porous foam Sintered nylon powder per se or reinforced with glass fibers may be used. controlled sintering of metals produce a controllable porous structure as does hot pressed ceramic. Many ot-her polymers -will qualify based on their physical properties, such as tensile strength, and sintering capabilities, primarily. Suitable candidates such as polyvinylchloride, tetrafluoroethylene and polystyrene are a small sample.

The escape of gas through the open structure while the sabot and projectile are in the gun barrel does not present a problem. In the FIGURE 4 configuration the passages developed in the solid material open only on the rear surface of the sabot. These passages may be shaped and oriented for specific effects.

The various features and advantages of the invention are thought to be clear from the foregoing description. Various other features and advantages not specifically enumerated will undoubtedly occur to those versed in the art, as likewise will many variations and modifications of the preferred embodiment illustrated, all of which may be achieved without departing from the spirit and scope of the invention as defined by the following claims;

We claim:

1. A disintegrating sabot for use with a projectile comprising a porous structure having means for entrapping propellant gas under pressure, said means being sufficiently frangible to be disintegrated by said gas in the absence of a restraining force.

2. A sabot as described in claim 1 in which the porous structure is made from open cell foam.

3. A sabot as described in claim 1 in which the porous structure is made from open cell, sintered material.

4. A sabot as described in claim 3 in which the sintered material is formed from plastic particles.

5. A sabot as described in claim 1 in which said porous structure is constructed by defining passages in the structure having surface openings on at least the rear surface of the sabot.

6. A sabot as described in claim 5 in which said passages are shaped to control the disintegrating action.

`7. A sabot as described in claim 5 in which said passages are oriented to control disintegrating action.

8. A method of removing a sabot from a projectile when the restraining force of a gun barrel is removed from the sabot comprising the steps of:

References Cited UNITED STATES PATENTS 2,811,901 11/1957 Barr 102-93 2,820,412 1/ 1958 Beeuwkes et al. 102-93 2,928,348 3/ 1960 Zisman et al 102-93 2,939,395 6/1960 Barr 102-93 3,040,662 6/ 1962 Zisman et al 102-93 3,092,026 6/ 1963 Williams et al 102--42 ROBERT F. STAHL, Pr'mary Exam'ner. 

